510 FOEAGE PLANTS AND THEIR CULTURE 



VIABILITY OF COWPEA SEEDS OP STANDARD VARIETIES WHEI<! 

 4, 7 AND 10 YEARS OLD 



Ordinarily, however, seed over two years old has lost 

 much of its viability. Seeds which have been wetted or 

 which are dead become duller and darker in color ; there- 

 fore uniformly bright colored seeds should be selected. 



623. Root system. The root system of the cowpea 

 is deep for an annual, there being a well-developed tap- 

 root with a number of large branch roots. These roots 

 spreading horizontally for a short distance, go deeply 

 into the subsoil, thus enabling the plant to draw freely 

 upon the minerals and water below the reach of the shal- 

 lower-rooted crops. 



At the Storrs Connecticut Experiment Station, an 

 investigation was conducted upon the amount of stubble 

 and roots, and distribution of the roots of the cowpea. 

 The following table gives the amount of roots at different 

 depths : 



